PURPOSE: The current study attempts to clarify the mediating role of cognitive function on the relationship between environmental pressure (pressure caused by negative parenting styles and dysfunctional school environments) and Internet Use Disorder (IUD); this study explores the effects of sex and left-behind children (LBC). METHODS: A cross-sectional sample of adolescents aged 12-15 years was recruited in 2018. A total of 3048 junior high school adolescents in rural areas of the Sichuan province in western China completed a series of psychological inventories, including the Adolescent Pathological Internet Use Scale (APIUS), the Junior High School Students' Perceived School Climate Inventory (PSCI-M), the Egna Minnen av. Barndoms Uppfostran (EMBU), and the Mental Health Screening Inventory for Children and Adolescents (MHS-C), for an analysis of IUD, school climate, parenting styles and cognition, respectively. RESULTS: Among the participants, 18.5% (N = 565) exhibited significant symptoms of IUD. The correlation analysis showed that IUD was positively correlated with parents' punishment, rejection and over-interference and academic pressure, whereas IUD was negatively associated with good teacher-student relationships, good schoolmate relationships and cognitive function scores. Structural equation modelling (SEM) showed that cognitive function partially contributed to the association between family and school pressures and IUD. DISCUSSION: Cognitive function is one of the mediating pathways through which environmental pressures may predict IUD among junior high school students. Interventions may target the mediating pathway of cognitive function to alleviate the negative impact of environmental pressure on IUD.